Heat as a factor in the penetration of cloth ballistic panels by 0.22 caliber projectiles

This report explores the possibility that heat plays a role in the penetrat ion of cloth ballistic panels by 0.22 caliber projectiles. We postulate tha t heat is generated by friction between the surface of the projectile and t he yarns, between yarns, and between filaments within a yarn in advance of and in the path of the projectile. Evaluations by light microscopy, polariz ed light microscopy, and scanning electron microscopy show heat-induced dam age in fibers in the path of and several layers preceding the layer at whic h a 0.22 caliber projectile comes to rest. Polarization microscopy of impac ted yarns reveals differences in birefringence within the fibers close to t he hole made by the projectile compared with the same fiber at a greater di stance from the hole. Heat is an energy sink, and depending on how, when, a nd where it is generated, can degrade the ballistic performance of the yarn s. The quantitative importance of heat in affecting ballistic panel perform ance is elusive: consequently, the discussion presented here is largely qua litative.